This invention relates to the field of valves for fluid conduits and, more particularly, to controlling the accidental or intentional drainage of fluid from a fluid conduit.
Prior to the present invention, conduits for delivering fluids have included a ball valve having a hole through its center that can be rotated to close the conduit to fluid flow or to open the conduit to fluid flow. Such a fluid delivery system is common for fuel delivery where fuel is delivered through a flexible conduit having a nozzle at one end. The flexible conduit is usually stored by winding it about a drum. The nozzle also commonly contains a spring-loaded check valve which functions as both an anti-theft device and an anti-drip device. The check valve is intended to prevent fuel from leaking or being intentionally drained from the conduit when the pump utilized to pressurize the fuel is inactivated. When the pump is inactivated, a meter for measuring the quantity of fuel delivered also is inactivated. By preventing drainage of fuel from the hose when the pump is inactive, the next customer of the fuel does not pay for the conduit to be filled before fuel is added to their tank. The check valve is effective for preventing such drainage of the conduit after fuel delivery is completed. The check valve also functions as an anti-drip device since it retains fuel within the conduit when the conduit is lifted at an intermediate point along its length while deploying or storing the conduit.
While the check valve provides some advantage to the user, its presence also is disadvantageous. First, the check valve restricts flow of fluid through the nozzle thereby increasing the time necessary to deliver a given quantity of fuel. Secondly, the check valve chatters, sometimes violently, during use. That is, the extent to which the check valve is opened depends upon conditions of fluid pressure and fluid velocity at the check valve. The chatter occurs when pressure in the conduit increases enough to open the check valve, but as the check valve opens, fluid velocity increases, and fluid pressure decreases, so that the check valve tends to close again. The variance of the check valve from a condition tending to open it to a condition tending to close it causes the chatter.
Accordingly, it would be desirable to provide a valve apparatus for a conduit which can prevent the intentional or accidental drainage of fluid from the conduit, without the attendant disadvantages of a check value.